1. Technical Field
This invention relates to new cosmetic compositions containing certain branched oligo-α-olefins and to the use of these branched oligo-α-olefins as oil components in cosmetic and pharmaceutical preparations.
2. Background Art
Consumers expect cosmetic skin- and hair-care emulsions to satisfy a range of requirements. Apart from the cleaning and skin-/hair-care effects which determine the intended application, value is placed on such diverse parameters as very high dermatological compatibility, good lipid-layer-enhancing properties, elegant appearance, optimal sensory impression and stability in storage.
Besides a number of surfactants, preparations used to clean and care for the human skin and hair contain, above all, oil components and water. The oil components/emollients used include, for example, hydrocarbons, ester oils and vegetable and animal oils/fats/waxes. In order to meet stringent commercial requirements in regard to sensory properties and optimal dermatological compatibility, new oil components and emulsifier mixtures are continually being developed and tested. A large number of natural and synthetic oils, for example almond or avocado oil, ester oils, ethers, alkyl carbonates, hydrocarbons and silicone oils, are used in the production of cosmetic or pharmaceutical preparations. A key function of the oil components—besides their care effect which is directly related to lipid layer enhancement of the skin—is to provide the skin of consumers with a non-sticky, almost instantaneous and long-lasting feeling of smoothness and suppleness.
The subjective feeling on the skin can be correlated and objectivized with the physicochemical parameters of the spreading of the oil components on the skin, as illustrated by U. Zeidler in the journal Fette, Seifen, Anstrichmittel 87, 403 (1985). According to this reference, cosmetic oil components can be classified as low-spreading (<300 mm2/10 mins.), medium-spreading (>/=300 to 1000 mm2/10 mins.) and high-spreading oils (>/=1000 mm2/10 mins.). If a high-spreading oil is used as the oil component in a predetermined formulation, the required feeling of smoothness of the skin is achieved very quickly and, where cyclomethicones, for example Dow Corning 245 fluid (Dow Corning Corporation) or Abil® B 8839 (Goldschmidt Chemical Corporation), are used, a velvety feeling desirable to the consumer is also obtained. Unfortunately, the experience does not last long because the high volatility of the last-mentioned structures means that the pronounced feeling of smoothness and hence the velvety feel disappear very quickly, leaving the skin with an unpleasant, dull feeling.
However, cyclomethicones have the advantage over other hydrocarbon-based emollients, such as very light mineral oils, polybutylenes (for example Arlamol® HD, ICI), ethyl hexyl cyclohexane (Cetiol®) S, Cognis Deutschland GmbH & Co. KG), that they have a very light feeling on the skin. Accordingly, there is a need for hydrocarbon-based oil components/emollients which combine the advantages of the cyclomethicones, such as a light feeling on the skin and good spreading properties, without having any of their disadvantages.
The use of tetraisobutylene in cosmetic compositions is known from EP 1 232 739 or EP 1 103 249.
The problem addressed by the present invention was to provide improved, high-spreading oil components and preparations containing them which would impart an almost instantaneous and relatively long-lasting feeling of smoothness to the skin and which would show good dermatological compatibility. In addition, the oil components would lend themselves to simple and stable incorporation in emulsions, would be hydrolysis-stable in the event of pH variations and would lead to low-viscosity compositions imparting a very light feeling on the skin. Another aspect of the stated problem was to provide oil components for antiperspirants/deodorants which would be comparatively unaffected by hydrolysis and would allow stable formulations in the presence of the astringent aluminium and zirconium compounds.